如何在 MySQL 中模拟数组变量?

2021-11-20 00:00:00 arrays set variables mysql temp-tables

似乎 MySQL 没有数组变量.我应该用什么代替?

It appears that MySQL doesn't have array variables. What should I use instead?

似乎建议了两种替代方案:集合类型标量和临时表.我链接到的问题表明前者.但是使用这些而不是数组变量是一种好习惯吗?或者，如果我使用集合，那么与 foreach 等效的基于集合的习语是什么?

There seem to be two alternatives suggested: A set-type scalar and temporary tables. The question I linked to suggests the former. But is it good practice to use these instead of array variables? Alternatively, if I go with sets, what would be the set-based idiom equivalent to foreach?

推荐答案

嗯，我一直在使用临时表而不是数组变量.不是最好的解决方案，但它有效.

Well, I've been using temporary tables instead of array variables. Not the greatest solution, but it works.

请注意，您不需要正式定义它们的字段，只需使用 SELECT 创建它们即可:

Note that you don't need to formally define their fields, just create them using a SELECT:

DROP TEMPORARY TABLE IF EXISTS my_temp_table;
CREATE TEMPORARY TABLE my_temp_table
    SELECT first_name FROM people WHERE last_name = 'Smith';

(另请参见不使用创建表从选择语句创建临时表.)

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